This invention relates to the field of mobile robots, specifically mobile robots with hopping mobility.
Robots are conventionally made mobile by rolling on wheels. Examples of wheeled robots include the Remote Telerobotic Vehicle for Intelligent Retrieval, and the Miniature Autonomous Robotic Vehicle from Sandia National Laboratories. See, e.g., Little et al., "Selective Retrieval of Buried Waste Using Mobile Manipulator Systems, American Nuclear society Fifth Topical Meeting on Robotics and Remote Systems, April 1993; Barry et al., "A Mobile Mapping System for Hazardous Facilities", American Nuclear Society Seventh Topical Meeting on Robotics and Remote Systems", April 1997. Other examples include NASA's Sojourner and the University of Michigan's A9. Wheeled robots are applied to a wide range of tasks.
Wheeled robots have limited ability to traverse large obstacles. Obstacles much taller than the robot's wheels can prevent passage. Also, obstacles with significant horizontal gaps such as trenches can also prevent passage. One solution is to use bigger wheels and a bigger wheelbase. Larger wheels and wheelbase require more drive power, so the entire robot must be larger. Many applications, however, have cost, size, space, or transportation constraints that limit the size of robot than can be used.
Advantages of Hopping Mobility
One alternative to wheeled mobility is hopping mobility. With hopping mobility, the robot jumps to move. Each jump is typically multiples of the robots dimensions in height and width. Accordingly, the robot can hop over obstacles much larger than a similarly sized wheeled robot could traverse. Hopping mobility can allow a small robot to traverse obstacles very large in relation to the robot itself, opening up applications that can not be addressed by wheeled robots.
At first glance, hopping as a means of mobility can seem relatively inefficient. However, this observation is based on intuition derived from the macroscale world. Macroscale concepts for mobility are often not applicable in smaller scales. This is because, as vehicle size is reduced, the relative number and size of obstacles that must be negotiated increases. At some point, obstacles must be laboriously negotiated that can be ignored in larger scales. For example, a wheeled vehicle covering grassy terrain simply rolls over the many blades of grass, but an insect covering the same terrain must climb over or around each individual grass blade. Similarly, if a macroscale vehicle were to attempt to traverse a region with obstacles similar in scale to those of blades of grass to an ant, existing common vehicle concepts would prove ineffective. This combination of increased relative obstacle size and inability of conventional methods to traverse these obstacles leads directly to the need for a new and innovative technique to cope with the problem.
Challenges in Hopping Mobility
Hopping robots pose many challenges unique to hopping mobility: linear actuator suitable for long trips, low energy steering and control, reliable low energy righting, miniature low energy fuel control, misfire tolerant single shot actuators, navigation and control. Hopping robots generally require a fast-acting linear actuator to drive the hop. Conventional wheeled robots use rotary actuators and therefore can rely on more mature actuation technology. Actuators for hopping robots must additionally be able to tolerate mis-actuations or misfires without relying on inertia of motion or flywheel effects common in wheeled robots and rotary actuation. A linear actuator suitable for a hopping robot must be able to resume operation after a single mis-actuation, else the robot will stall completely on its first fault.
Hopping robots generally will require many hops to traverse a significant distance, so low energy steering and control are important. Wheeled robots can steer by directional control of wheels or by skid steering, using the same energy source for steering as is used for mobility. Hopping mobility does not lend itself to the same dual use as readily.
Wheeled robots generally remain in a given orientation, e.g., on the wheels substantially parallel with the ground. Hopping mobility, however, can subject the robot to unpredictable forces during hopping that can result in unpredictable orientations on landing. Hopping robots therefore can require the ability to return the robot to a known orientation after each hop, preferably with minimal energy consumption.
Accordingly, there is a need for a hopping robot that addresses the challenges specific to hopping mobility.